Too Long; Didn't Read
Selenium is a web browser automator for web scraping. When used as scraper, from it you'll get a browser like Chrome or Firefox navigating to the webpage you want, interacting with it the way you want and extracting all the information that you might need. Selenium controles a browser (Chrome, Firefox etc...) through a driver, each browser has it's own drivers. The tutorial is a basic tutorial for you to get running with Selenium as a Web Scrapper, do not take it as an exhaustive tutorial.